DESCRIPTION: (adapted from applicant s abstract): The U1-70kDa ribonucleoprotein, a prevalent autoantigen in rheumatic disease patients, undergoes proteolytic cleavage in apoptosis. A model of autoimmune diseases proposes that modified forms of self antigens can lead to recognition of previously cryptic epitopes, allowing an auto-reactive immune response to evolve. Thus, apoptotically modified Ul-70kDa is a candidate antigen that may be involved in the evolution of autoimmune rheumatic diseases. The long-term objective of this application is to develop an independent program of research that leads to improved diagnosis, treatment, and prevention of rheumatic diseases, based on an improved understanding of the contribution of apoptotically modified self antigens to the generation of autoimmune responses. The following specific aims will examine the role of apoptotic Ul-70kDa in autoimmune disease. First, it will be determined whether apoptotic Ul-70kDa is antigenically distinct from intact Ul-70kDa. Sera from patients with intact Ul-70kDa antibodies will be tested for antibodies specific for the apoptotic form of U170kDa by ELISA and immunoblot. Immunoglobulins generated from Fab phage expression libraries selected against apoptotic Ul-70kDa will also be screened for apoptosis-specific Ul-70kDa reactivity. Epitope mapping will be performed with all apoptotic Ul-70kDa specific antisera and Fab to identify the immunologically distinct areas on the apoptotic form of the antigen. Second, in a large cohort of rheumatic disease patients from whom multiple serial blood samples have been drawn, it will be determined whether anti-apoptotic U170kDa responses precede anti-intact Ul-70kDa immune responses. As a result of this research, the contribution of apoptotic U1 -70kDa epitopes to the immunopathogenesis of rheumatic diseases will be elucidated. Assays for antibodies to apoptotically modified Ul-70kDa with potential clinical relevance to the diagnosis and management of rheumatic diseases, will be developed. In the future, this work may lead to the development of specific immunotherapy strategies for the treatment of Ul-70kDa-associated rheumatic disorders.